1. Field of the Disclosure
This disclosure relates generally to an air purification system. More specifically, the present disclosure relates to an air purification device or system comprising photocatalysts that resist or slow deactivation of the photocatalyst material.
2. Description of the Related Art
Buildings may utilize air purification systems to improve the quality of indoor air, thus enabling the building operator to decrease ventilation to the outdoor environment, create a cleaner indoor environment, or both. The quality of indoor air is often improved through air purification using gaseous contaminant removal technologies. Photocatalysis is a proven technology for removal of gaseous airborne substances such as volatile organic compounds (VOCs) including toluene, formaldehyde, and other contaminants from the air supply.
Photocatalytic air purifiers utilize a substrate or cartridge containing a photocatalyst, that interacts with airborne oxygen and water molecules to form hydroxyl radicals when placed under an appropriate light source. The radicals then attack the contaminants and initiate the oxidation reaction that converts them into less harmful compounds, such as water and carbon dioxide. It is further believed that the combination of water vapor, suitably energetic photons, and a photocatalyst also generates an active oxygen agent like hydrogen peroxide that can act over a distance of several microns from its source. This active agent also contributes to the oxidation of the organic contaminants.
Deactivation of the photocatalyst limits the effectiveness of photocatalytic air purifiers. Currently available systems have been found to exhibit a significant loss in catalytic ability over time. This can create significant expense for the operator of the air purification system, due to the labor and equipment costs associated with cleaning and/or replacing the photocatalyst cartridges.
Accordingly, there is a need for an air purification system or photocatalyst that can resist deactivation in general and/or can resist deactivation due to sudden and/or prolonged rises in contaminant concentration.